Traumatic head injury is the leading cause of brain damage in previously healthy young people. It is estimated that 400,000 new cases are hospitalized for head injury each year in the United States. In addition to the dollar cost, the significance of head injury as a major health and social problem comes from the fact that the numbers involved are large, the population affected is young, and if the victims survive, they can expect a normal life span but a possibility of reduced quality of life resulting from the consequences of brain damage. The major aim of this application is the determination of head injury outcome and factors predictive of outcome. Predictive factors that will be investigated include head injury severity, severity of other system injuries (as assessed by the Abbreviated Injury Scale) and pre-existing conditions. We will also examine the extend of rehabilitation treatment use and, if fair evaluation is possible, the efficacy of treatments. We propose to satisfy the aims of this application by performing secondary analyses based on three longitudinal studies of head injury outcome, two of which were supported by the National Center for Health Services Research and one by the National Institutes of Health. These three studies involve 500 adult prospectively studied representative head injured cases and 280 comparison subjects. All subjects have been carefully studied with the same study protocol. All subjects were followed to one year and the severely head injured cases to two years post injury. Additional aims of this application involve examination of the reliability of neuropsychological measures commonly used to assess brain damage. In addition to our comparison subjects, 200 normal controls from the University of California at San Diego will be available for the reliability studies. The specific aims of this grant involve new questions that have arisen during the analyses of the prior studies as well as questions of long- standing interest that require larger sample sizes than any of the individual studies has been able to provide. Knowing the expected outcomes form head injury and being able to predict them accurately provides benefits in a number of areas including evaluation of treatments, allocation of health services, improved clinical decisions and assisting patients and families in planning for the future.